Control valve for variable displacement compressor

Abstract

A control valve for a variable displacement compressor that is mounted on the variable displacement compressor to control pressure within a hermetic crankcase to thereby change the discharging capacity of a refrigerant.

What is claimed is: 
     
       1. A control valve for a variable displacement compressor, which is mounted on the variable displacement compressor to control pressure within a hermetic crankcase thereof to thereby change discharging capacity of refrigerant, comprising:
 a body having a refrigerant passage formed therethrough; 
 a valve section including a valve element moving to and away from a valve seat formed in the body so as to adjust a flow rate of refrigerant when part of refrigerant discharged from the variable displacement compressor is caused to flow into the crankcase, and a shaft configured to be axially slidably supported by the body and support the valve element such that the valve element can be caused to operate in unison therewith; and 
 a solenoid including a core fixed within the body, a plunger for moving the valve element forward and backward within the body via the shaft so as to cause the valve element to open and close, and a solenoid coil for generating a magnetic circuit including the plunger and the core by electric current supplied from outside, 
 wherein the plunger is formed by arranging a first plunger opposed to the core, and a second plunger to which an end of the shaft, opposite to the valve element, is connected, in series in an axial direction, the plunger being formed by arranging a pressure-sensing member for sensing suction pressure from a suction chamber, and a hollow cylindrical magnetic member for fixing the pressure-sensing member to the solenoid, between the first and second plungers, 
 wherein the first plunger is configured to be urged in a direction away from the core, and support the second plunger in an axial direction when the solenoid is energized, and 
 wherein the second plunger includes a small-diameter portion inserted into the magnetic member such that a predetermined space is formed therebetween, and a large-diameter portion radially outwardly extending from the small-diameter portion and having an opposed surface formed thereon which is axially opposed to an opposed surface of the magnetic member, the second plunger being urged in a direction away from the first plunger, while the magnetic circuit being formed via the opposed surfaces during energization of the solenoid. 
 
     
     
       2. The control valve for a variable displacement compressor according to  claim 1 , wherein an elastic member formed of a non-magnetic material for urging the second plunger in the direction away from the first plunger is disposed between the small-diameter portion of the second plunger and the magnetic member. 
     
     
       3. The control valve for a variable displacement compressor according to  claim 1 , wherein the first plunger and the core have respective tapered surfaces having complementary shapes to each other formed on opposed surfaces thereof. 
     
     
       4. The control valve for a variable displacement compressor according to  claim 1 , wherein the second plunger and the magnetic member have respective tapered surfaces having complementary shapes to each other formed on the opposed surfaces thereof.